Liquid hydrocarbon fuels containing metal complexes of betaines as antistatic agents



United States Patent 3,116 125 LIQUID HYDROCARBQPi FUELS CONTANNG METAL CGMPLEXES 0F BETAINES AS ANTE- STATIC AGENTS Philip Lee Bartlett, Wilmington, Dei, and Gastao Etzel,

Collingswood, N.J., assignors to E. I. du Pont de Nemonrs and Company, Wilmington, Del., a corporation of Delawane No Drawing. Filed Mar. 8, 1961, Ser- No. 94,127 3 Claims. (Cl. 4468) This invention is directed to the treatment of hydrocarbons, such as distillate fuels, which tend to accumulate potentially hazardous electrostatic charges in service. A number of explosions and fires that have occurred in recent years during the bulk handling of distillate fuels and solvents have been attributed to the accumulation (and subsequent discharge) of static electricity in the systems involved. Some handlin conditions which contribute to the rapid generation of dangerous charge levels are rapid flow of fuel through pipelines and hoses, splash filling of receiving vessels (storage tanks and seagoing tankers), and, mixing of the fuel and water.

In recent years, the use of additives has shown some promise in minimizing the accumulation of static electricity. These additives should be effective in small concentrations and have no adverse effects on the hydrocarbon products, especially jet fuels, where stringent specifications have to be met.

Polar compounds such as metal or ammonium (including quaternary ammonium) salts of inorganic and organic acids, e.g. of phosphorus, sulfur and carboxylic acids have been suggested as antistatic additives for liquid hydrocarbon fuels; such compounds are, however, deficient in one or another aspect in meeting specifications of fuels, especially jet fuels. For instance, the ammonium salts of organic acids create severe emulsion hazards, While the inorganic salts have poor hydrocarbon solubility.

It is, therefore, an object of the present invention to provide novel anitstatic agents which are significantly effective, in liquid hydrocarbons, in minimizing the accumulation of static electricity. It is a further object of this invention to provide novel antistatic compositions which do not adversely affect the properties of liquid hydrocarbon fuels.

These and other objects will become apparent in the following description and claims.

The novel compositions of the present invention are betaine complexes containing small amounts of two diferent metals, which together are more effective as antistatic additives than either metal complex alone. Contrary to previous concepts that the antistatic agent be non-metallic in order to promote fuel stability and avoid formation of combustion deposits, it is surprising that the compositions of the present invention have no adverse effects on the fuel and do not further the formation of combustion deposits. It is also surprising that the particular combination of metals in the present novel compositions causes an unexpected increase in the electrical conductivity of the static-prone hydrocarbon. This extraordinary effect is due to the combined action of the complex of the two metals with the betaine as hereinafter described, and is much greater than that produced by the betaine alone or with only one of the metals present.

More specifically, the present invention is directed to an antistatic additive for liquid hydrocarbons boiling in the distillate fuel range comprising (1) a liquid hydrocarbon carrier, (2) from 20-60% by Weight of a hydrocarbonsolu ble metal complex of at least one betaine of the formula (3) calcium or chromium ions and (4) an alkali metal ion, where R is an aliphatic hydrocarbon radical, R and R are lower alkyl, R is a saturated divalent aliphatic hydrocarbon radical and x is 0 or 1, the betaine containing 1.l35 carbon atoms.

A preferred embodiment of the present invention is the heretofore described novel antistatic additive wherein the total metal content does not exceed 6% by Weight of the metal betaine complex, the Ca++ or Cr+++ is present in amounts of 0.05 to 5.0% and the alkali metal ion is present in amounts of 0.001 to 1.0% by weight of the metal betaine complex.

The preferred limits of Ca++ or Cr+++ are 0.5 to 2.5% and of the alkali metal ion, 0.025 to 0.5%, expressed in terms by Weight of the described metal betaine complex.

Another embodiment of the present invention is a liquid hydrocarbon boiling in the distillate fuel range containing an antistatic quantity, or" from 0.04 to 30 pounds, preferably 0.4- to 10 pounds, per 1000 barrels of hydrocarbon, of a metal betaine complex as heretofore defined.

The structure of the betaine component utilized according to the present invention is represented by the formula Where x is 0 or 1, R is an aliphatic hydrocarbon radical containing up to 20 carbon atoms and may be saturated or unsaturated, straight chain or branched chain. Representative examples are methyl, butyl, hexyl, decyl, dodecyil, tridecyl, octadecyl, octadecenyl, octadecadienyl and 3,7-dimethyl-2,6-octadienyl. Preferably R has at least 10 carbon atoms. R and R may be the same or different C to C alkyl radicals, e.g. methyl, ethyl, propyl, butyl and amyl, preferably C to C R is an alkylene radical, preferably methylene, or an alkylidene radical having up to 17 carbon atoms, such as ethylidene, propylidene, undecylidene, tridecylidene and heptadecylidene.

The alkali metal may be sodium, potassium, lithium or cesium, but for practical purposes, sodium and potas sium are preferred.

Representative betaine components of the invention in which x in the formula is 0 and R is an aliphatic hydrocarbon radical attached to nitrogen of a dialkyl glycine radical are N-lauryl betaine (i.e. N-lauryl-ILN-dimethyl glycine), N-hexadecyl betaine, N-octadecyl betaine, N- octadecenyl betaine, N-lauryl-N,N-dipropyl glycine. (Disclosed in U.S. Patent 2,129,264.)

Betaines in which x is l are N-(2-hydroxy-3 butyloxypropyl) betaine, N-(2-hydroxy-3-decyloxypropyl) betaine, N-(2-hydroxy-3-lauryloxypropyl) betaine, N-[2- hydroxy 3 (3,7 dimethyl 2,6 octadienyl) oxypropyl] betaine, N-(2-hydroxy-3-tridecyloxypropyl) betaine, N (2 hydroxy 3 octadecenyloxypropyl) N,N diethyl betaine, and the correspondingly substituted N,N- dipropyl betaine.

It has been found that in the conventional methods of preparation of betaines where a metal containing reagent has been used, a product results containing a small amount of the metal complexed with part of the betaine. Thus in the preparation of the antistatic agents of the present invention, a simple method may be employed for the preparation of the betaine complexes wherein both alkali metal and polyvalent metal reagents are used. This method consists in reacting an alkali metal cyanide with formaldehyde to form glycolyl nitrile, adding dialkylamine to form dialkylaminoacetonitrile which is then hydrolyzed with calcium hydroxide to the corresponding dialkylglycine salt. The chromium salt is formed by a reacting the glycine with a chromium salt, as illustrated in the following equations:

(CHshNCHzC O OH [(0113) 2NCI'I2C O OhCr This is further reacted with the condensation product of an alcohol and epichlorhydrin or an alkyl halide to form a betaine complex containing both an alkali metal and polyvalent calcium or chromium. For example,

The alcohol heretofore referred to contains preferably 10 to 20 carbon atoms. Available alcohols of this type include the Lorol fatty alcohol mixtures, e.g. Lorol 5 which contains alcohols having -18 carbon atoms with lauryl alcohol predominating; Ocenol fatty alcohols, e.g. Ocenol P which is principally oleyl alcohol; geraniol (3,7 dimethyl 2,6 octadienol); oxo-alcohols, which are mixtures of branched chain primary alkanols, e.g. oxo-tridecanol.

These N (2 hydroxy 3 alkoxypropyl) N,N-dialkyl betaine metal complexes may also be prepared by condensing the alcohol with epichlorhydrin and reacting the intermediate condensation product thus obtained with an alkali metal salt of an N,N-dialkyl glycine. In a similar manner, an alkyl halide can be reacted with an alkali metal salt of an N,N-dialkyl glycine. The betaine obtained contains a very small amount, less than 1%, of the alkali metal used in the previous step, in complex form with the betaine. This betaine-alkali metal complex may then be heated with calcium oxide, hydroxide or a salt such as sulfate, oleate, petroleum sulfonate or tallate to form a calcium containing complex with the alkali metal-betaine compound, or with chromium chloride or sulfate to form the chromium-alkali metal betaine complex.

Alternatively, the bimetal complex of the present invention may be obtained by preparing a calcium or chromium salt of the N,N-dialkyl glycine and reacting with the condensation product of the alcohol with epichlorhydrin or with an alkyl halide. The product obtained contains calcium or chromium, as the case may be, in complex form with the betaine. This betaine complex may then be blended with the alkali metal betaine complex, obtained as described in the previous method before treatment with the polyvalent metal compound, either in equal proportions or in proportions such that the metal content is within the prescribed limits.

Representative examples illustrating the present invention follow.

Methods of preparation of representative antistatic agents of the invention are illustrated by the following:

Example I The reaction vessel is charged with 39 moles of Water. Hydrogen peroxide is added to give a positive test with cadmium iodide starch paper. Calcium hydroxide is added to give a positive test to Clayton yellow test paper. Sodium cyanide (1.3 moles) is added and the mixture is agitated at 2.5 i2.5 C. until a clear solution is obtained.

betaine.

The temperature is raised to 7.5 L2.5 C. and 1.45 moles of formaldehyde (as 37% aqueous solution) are added as rapidly as possible, maintaining the temperature limit. The mixture is agitated at 7.5 :25 C. for /2 hour after addition of formaldehyde. The percent of free cyanide is determined and should not exceed 0.3%. Hydrogen peroxide is added to give a positive test to cadmium iodide starch paper. Sulfuric acid (40%) is added until the pH reaches 7.6, maintaining the temperature at 7.5 *-2.5 C. during addition of the acid. The reaction mixture is agitated for 15 minutes after the addition of the acid. Dimethylamine (1.45 moles as 40% aqueous solution) is added at 7.5 $2.5 C. Hydrogen peroxide is added to give a positive test to cadmium iodide starch paper. The mixture is heated to 15 C. and temperature maintained at l520 C. for 30 minutes and then is cooled to 1015 C. and 1.6 moles of calcium hydroxide are added. Water (1 mole) is added and the temperature is allowed to rise to 2025 C. and maintained for 30 minutes. The temperature is raised to reflux and maintained for 6 hours. Xylene (8.6 moles) is added and water is removed by azeotropic distillation. Azeotroping is stopped at 112- 115 C. Potassium iodide (0.005 mole) is added to the vessel and, over a period of 2 hours, 1 mole of 2-hydroxy- 3-o1eyloxypropyl chloride is added. The temperature is raised to 115 125 C. and maintained for 12 hours. The reaction mixture is cooled to 50 C. and 2 moles of methyl alcohol are added to facilitate salt filtration. chloride and potassium iodide are removed by filtration and the reaction mass concentrated to about 50% active ingredient by distilling off methanol and xylene. After analyzing for percent active ingredient by HClO titration the product is diluted to 40% active ingredient using 90/10 mixture of xylene/methanol. The yield of the sodium and calcium containing complex of N-(Z-hydroxy- 3-oleyl0xypropyl) betaine is 95% of theory.

Example 2 The reaction vessel is charged with 5.07 moles of NH free glycine, 10.14 moles of formaldehyde (as 37% aqueous solution) and 30.42 moles of formic acid (88%). The temperature is raised to about 40 C. at which point the exothermic reaction starts and the temperature rises to about 55 C. Slowly the reaction temperature is increased to 60 C. and maintained for 17 hours. Concentrated HCl (506 ml. sp. gr. 1.18) is slowly added and the mixture stirred 15 minutes after addition. The reaction mass is vacuum stripped, leaving a brownish-red crystalline solid. The crystals are repeatedly washed with glacial acetic acid until light tan in color. The N,N- dimethyl glycine hydrochloride is sucked dry under vacuum in a filtering funnel (Biichner). The yield is about 95%.

N,N-dimethyl glycine hydrochloride (2.15 moles), Na CO (2.15 moles), 1290 ml. of isopropanol and 64 ml. distilled Water are combined and refluxed 2 /4 hours C.). 2-hydroxy-3-lauryloxypropyl chloride (2.15 moles 3% excess) and KI (7.2 gm.) are added and the mixture refluxed at 84 C. for 24 hours. After cooling, the salt is filtered off (84.5% of theory). The isopropanol and water are vacuum stripped to a pot temperature of 120 C. One liter of anhydrous isopropanol is added to the vessel and the temperature raised to reflux (86.5 C.) for 2 hours. After cooling, additional salt is filtered off (14.9% of theory, total salt recovered is 99.4% of theory). The isopropanol is vacuum stripped to a pot temperature of 102 C. leaving an amber wax, the sodium complex of N-(2-hydroxy-3-lauryloxypropyl) The betaine was dissolved in 10 mixture of xylene/methanol so as to give an approximately 50% active ingredient solution. After determining the percent of active ingredient by HClO titration, the betaine solution is diluted to 40% active ingredient with additional 90/ 10 xylene/methanol. The yield of betaine is 97% of theory.

The sodium One mole of the betaine complex obtained as above described is heated at 100210" C. for 4- hours with one sixth mole of Cr (SO After cooling, the sodiumchromium complex is filtered free of any insolubles.

The variables of the metal betaine complex utilized according to the present invention are so chosen that the complex will be soluble in the hydrocarbon media to the extent of at least 0.04 pound, preferably 0.4 pound, per 1000 barrels of the hydrocarbon. The quantity of the antistatic agent needed to minimize the accumulation of static electricity in the hydrocarbon substrate will vary with tie particular betaine complex and the particular hydrocarbon product, and will depend in general on how prone such hydrocarbon is to accumulate static electricity. Normally, from about 0.04 to pounds of additive, and preferably 0.4 to 10 pounds per 1000 barrels will be employed. Larger quantities, elg. 30 lbs/1000 bbls. are operable ifor antistatic effects, but are usually unnecessary. Also such unduly large quantities tend to promote the water emulsification of distillate fuels. While small quantities, e.g. 0.04 lb./1000 bbls., may also be operable, they do not always provide the desired degree of protection.

It should be understood that the presence of the antistatic agent in the hydrocarbon substrate does not do away with the need for adequate grounding of the equipment for containing and handling the hydrocarbon product. The antistat apparently functions to minimize the accumulation of static electricity in the hydrocarbon product by conducting the charge (as it tends to build up in the hydrocarbon) from the hydrocarbon to the grounding means.

The use of the betaine complex antistatic agents of the present invention is applicable to any liquid hydrocarbon that boils in the distillate fuel range and is prone to accumulate static electricity in service. These include hydrocarbon solvents and distillate fuels, representative examples of which are the solvent naphthas, Varsols and Stoddard solvent, isooctane, both raw and refined kerosenes, gasoline (both automotive and aviation), jet fuels (JP-4, JP-S and JP-6) diesel fuel and heating oil.

For convenience in handling, the betaine antistatic agents may be added to the hydrocarbon substrate as a concentrate in a suitable carrier, which is preferably a liquid hydrocarbon. For example, a to 60%, usually about 40%, by weight of N-lauryl betaine in xylene or kerosene is a preferred form of the antistatic additive.

The antistatic additives may be used in the presence of other additives that the hydrocarbon product may normally contain, such as the approved oxidation and rust inhibitors for the jet fuels.

The herein described betaine complexes are effective antistatic agents in practical use concentration and in general do not promote the tendency of the fuel blends containing them to em-ulsify when mixed with water. This is particularly surprising and important since betaines in general are regarded as surface active agents and it is known that polar additives that are surface active, such as quaternary ammonium salts, when used in concentrations required for antistatic activity, have the major disadvantage of failing to meet water tolerance specifications of fuels, such as jet fuels.

The fuel containing the antistat according to the present invention passes the Standard Water Tolerance Test as described in Method 3251 of Federal Specification VV-L-791C. The test consists of shaking ml. of the fuel and 20 ml. of water, (containing a pH 7 phosphate buffer) in a ml. stoppered graduated cylinder for two minutes, and allowing to stand for five minutes. To pass the test, the water and oil phases must break cleanly within the five minute standing period. Any emulsion or lace in the oil, or precipitate at the interface leads to a fail rating.

Furthermore, the herein described improved fuel composition shows no tendency to accumulate electrostatic charge even after the fuel has been shaken with as much as 5 volume percent of water.

It has been established, that to safeguard normal handling and refinery operations, the conductivity level of hydrocarbon products should be raised to a value of about 1000 picomho/m. or 1000 10- ohrrr cm The most dangerous products are those having conductivities below 10 picomho/m. Expressed in this unit, the conductivity of white spirit is 0.02 to 1, motor gasoline 0.3 to 10, kerosene 0.02 to 40 and gas oil 600 to 1200, the presence of contaminants affecting static generation.

The method used for determining the conductivities of petroleum products is a widely accepted method described in the Journal of the Institute of Petroleum 44, 380 (November 1958). The apparatus consists of a stainless steel condenser of standard size which contains a sample of the hydrocarbon liquid as the dielectric. One electrode consists of a stainless steel sphere suspended in the liquid at the center of the container and the other electrode is formed by the container. An external potential of to volts is applied to the central electrode, and the time taken for this voltage to decrease to a standard fraction of its initial value is measured. Knowing the capacitances in the system and the dielectric constant of the liquid, the conductivity of the hydrocarbon sample is calculated.

A concentrate of the metal betaine complex was prepared consisting of a xylene solution containing 40% by weight of the complex. Conductivities were determined by the heretofore described method of a hydrocarbon fuel containing varying amounts of the antistat per 1000 barrels of fuel. Results of the measurements are given in the following table.

Antistat Conductivity in picomho/rneter Hydro- Percent metals carbon Lbs. of autistat per 1,000 R(OCH CHOHOHz)XN+CHTOOO- bbls. hydrocarbon z=1; R= 0.33 Na; isooctane 0.1 9,960 29. 804

:I:=1; R= 0.33 Na; JP-4 4.6 1, 566 5, 500

11:1; R: 0.33 Na; JP5- 0.2 4, 200 14,070

z=1; R= 0.10 Na; 0.2 1,431 4, 245 1:1; R: 0006 Na; isooctane 0.1 z=1; R= 0.0015 K is0oetane 0. 1 513:1; R: 0.003 K isooctane 0.1 z=1; R: 4.5 Ca' isooctane (.1 1:1; R: 1.58 Na isooctane 0.1 13-4-- 4. 6 0.2 :r=1; R= 3.6 Cr 0.2

z=0; R= 0.05 K; 0.6 Ca 0.2 1,248 3,711

x=0;R= 0.13K 0.2 45 142 The unexpected effect of the combination of an alkali metal and calcium or chromium with a betaine on the conductivity of the [hydrocarbon fuel is shown in the preceding table. It can readily be seen that the individual conductivities of a fuel containing a bet-ante and one metal only, either an alkali metal, or calcium or chromium, are far below the values for the combined metal antistat. It is surprising that the combination of the two metals, when present together, produces such a high increase in conductivity, which is considerably greater than the sum of the conductivites of a fuel containing a betaine alkali metal complex and one containing a betaine calcium or chromium complex. Betaine metal complexes containing both calcium and chromium do not show the surprisingly high conductivities of the compositions of this invention. On the other hand, addition of an alkali metal ion to a betaine containing both calcium and chromium did in crease the conductivity remarkably and such compositions are meant to fall within the scope of this invention.

The antistats of the present invention are significantly effective in all distillate fuel oils in preventing the accumulation of static changes. By the addition of small amounts of the herein described antistat, hazardous conditions such as fires and explosions, in handling fuel oils can be greatly reduced.

In the practice of the present invention, the betaine antistatic agents may be added to the hydrocarbon substrate herein described as a concentrate in a carrier such as benzene, toluene, ethyl benzene, Stoddard solvent, mineral oil, diesel oil and fuel oil. These agents will normally be present in said concentrate in an amount within the range of 20 to 60% by weight. It would be economically unfeasible to go below 20%. The betainemetals complex itself is a waxy solid and concentrated solutions are quite viscous and hard to handle, especially at low temperatures. The upper limit of about 60% is at the borderline of ready commerical use. Much more con centrated solutions could be prepared and used in the practice of this invention, but would be too viscous for convenient handling.

As heretofore described, the useful range for amounts of Ca or Cr ions varies from 0.05% to with the preferred range being 0.5 to 2.5 Below 0.05% of these metals little, if any, beneficial effect due to the presence of the metals is demonstrated. In most cases, 0.5% is needed to obtain an appreciable effect. The exact amount of metal needed to obtain a certain conductance will vary from fuel to fuel. The upper limit of 2.5% is preferred for economic reasons, since beyond this level little additional increase in conductance is obtained by additional amounts of metal, although with some fuel types up to about 5% may be needed.

The alkali metal ion is present in an amount within the range of 0.001 to 1.0% by weight of the metal betaine complex. Little, if any effect was noted below 0.001% and the upper limit of 1.0% alkali metal is dictated by solubility problems, since it is difficult to prepare a soluble betaine-metals complex having more than 1% alkali metal and it is preferred to have no more than about 0.5% alkali metal, for this reason. A practical and preferred lower limit is 0.025% alkali metal.

It is understood that the preceding examples may be varied by one skilled in the art, within the scope of the total specification, to achieve essentially the same results.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An antistatic additive for normally liquid hydrocarbons boiling in the distillate fuel range, said additive consisting essentially of a liquid hydrocarbon carrier and from 20 to by weight, of a hydrocarbon-soluble metal complex consisting essentially of (1) at least one betaine of the formula wherein R is an aliphatic hydrocarbon radical, R and R are lower alkyl, R is a saturated divalent aliphatic hydrocarbon radical and x is an integer from O to 1, said betaine containing from 11 to 35 carbon atoms,

(2) ions selected from the group consisting of calcium,

chromium, and mixtures of said ions and (3) an alkali metal ion.

2. An antistatic additive according to claim 1 wherein the total metal content does not exceed 6% by weight of the metal betaine complex, the ions of (2) being present in an amount within the range of 0.05 to 5.0% and said alkali metal ion being present in an amount within the range of 0.001 to 1.0% by weight of the metal betaine complex.

3. A normally liquid hydrocarbon boiling in the distill-ate fuel range containing an antistatic quantity of from 0.04 to 30 pounds, per 1,000 barrels of said hydrocarbon, of the antistatic metal betaine complex of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 2,129,264 Downing Sept. 6, 1938 2,217,846 Orthner et al. Oct. 15, 1940 2,951,751 McDermott Sept. 6, 1960 2,974,027 -Di Piazza Mar. 7, 1961 FOREIGN PATENTS 749,898 Great Britain June 6, 1956 214,798 Switzerland Aug. 16, 1941 

1. AN ANTISTATIC ADDITIVE FOR NORMALLY LIQUID HYDROCARBONS BOILING IN THE DISTILLATE FUEL RANGE, SAID ADDITIVE CONSISTING ESSENTIALLY OF A LIQUID HYDROCARBON CARRIER AND FROM 20 TO 60%, BY WEIGHT, OF A HYDROCARBON-SOLUBLE METAL COMPLEX CONSISTING ESSENTIALLY OF (1) AT LEAST ONE BETAINE OF THE FORMULA 